This invention relates to methods of removing small amounts of hydrazine from a substance.
Poly(N-vinyl-2-pyrrolidinone) (PVP), also known generically as povidone, is widely used in the medical and food industries. See, for example, Kirk, Othmer Encyclopedia of Chemical Technology, Third Edition, Vol. 23, 1983, John Wiley & Sons, p. 966-979, and The Handbook of Water Soluble Gums and Resins by Robert L. Davidson, 1980, McGraw-Hill. PVP is a polyamide that possesses unusual complexing and colloidal properties and is physiologically inert. Several grades are manufactured and sold under a variety of trade names.
PVP was first developed in Germany during the 1930's and was widely used by the Germans as a blood plasma extender during World War II. It has since been used in a variety of other pharmaceutical applications because of its outstanding properties.
Hydrazine (N.sub.2 H.sub.4) is a dibasic compound having a strong odor resembling that of ammonia. It is a strong reducing agent and easily forms derivatives of many organic compounds. It can be determined by well known chromatographic techniques, such as those discussed in Canadian J. Pharm. Sci. 16 (1981) p 15-19.
A sensitive new generation of analytic instrumentation has allowed the detection of trace amounts of hydrazine in pharmaceutical grade PVP. It would be advantageous to reduce the amount of hydrazine in PVP to below the limits of detectability with available analytic instruments.
A suitable removal method is characterized by four features. First, the method should not take much time; second, it should not add new impurities; third, all detectable hydrazine should be removed; and fourth, the PVP should not be deleteriously modified.
A method that satisfies the above four criteria is contacting the contaminated PVP with ozone, since it is known that ozone readily reacts with hydrazine, see J. Am. Chem. Soc. 31 (1909) p. 790. Such a method rapidly removes the hydrazine while adding no new contaminants, since the reaction products of hydrazine and ozone are water, molecular oxygen and molecular nitrogen.